The three-sided purple structures, which are covered in a sticky lure, are designed to attract the invasive Asian insects, which are a threat to native ash trees. The traps have been placed by the USDA’s Animal and Plant Health Inspection Service (APHIS) as part of a national effort to monitor the spread of the small metallic green beetles, the larvae of which feed under the bark of the tree.

According to Hargrave, the insects, which are not native to Asia, first appeared in the United State in 2001, when they were discovered around Detroit. Without natural predators to keep them in check, she says the invasive beetle has killed tens of millions of ash trees in 15 states and two Canadian provinces. As of last year, seven of New York’s 62 counties were affected by 6 known infestations. Two more exist over the Canadian border.